The invention is directed to a sewing or embroidery machine, and more particularly to a sewing or embroidery machine with a hook, which oscillates or rotates about a hook rotational axis, whose drive shaft is drivingly connected with a drive of the sewing machine.
The comparatively very minimal supply of bobbin thread in relation to the needle thread, which can be made available in any amount outside the sewing machine, forces the operator of a sewing or embroidery machine to remove the bobbin from the hook in the lower arm, flat bed, or base of the sewing machine and to replace it with a new one. In a sewing machine with a hook that rotates or oscillates about a vertical axis, to change the bobbin, the material to be sewn must be lifted from the needle plate and the bobbin must be detached from the hook with little or no sight of the bobbin and then the new bobbin must be inserted again into this hook. Also for hooks, which rotate or oscillate about a horizontal axis, the forward exchange of the bobbin requires a certain amount of skill, although for accessing the hook, the material to be sewn is disturbed less than for the first mentioned example. However, viewing the hook is made more difficult during the bobbin changing process. The tight spatial relations and the usually very small cross-sectional opening in the lower arm, through which the bobbin case containing the bobbin can be removed from the hook housing with two fingers, also makes the use of bobbins with a large amount of thread more difficult.
This disadvantage applies to all sewing machines, both household sewing machines and also industrial sewing machines, which require a fast bobbin exchange anyway for economical reasons.
Automatic bobbin or hook changing systems are already known for industrial or commercial machines.
From DE-C1-196 53 296, an embroidery machine with a hook exchanger is known, for which the entire hook, including bobbin and bobbin case, is removed from the hook drive by a handling device and is replaced by a new hook with a full bobbin. In a first configuration of this known arrangement, the handling device includes a revolver carrier, on which the hook with the empty bobbin is set and is pivoted about an axis after being removed from the hook drive and then the full hook is set on the hook drive. Here, the revolver of the handling device completes not only a rotational movement, but also simultaneously a translational movement. Such an arrangement is definitely able to replace an empty bobbin with a new one within a short time period. However, then the hook with the empty bobbin must be removed from the handling device and the bobbin must be detached from the hook and replaced by a new, full bobbin. Such an arrangement cannot be used in a household sewing machine with a free arm for reasons of space and also the costs for such a hook changing device are out of proportion with the costs of the sewing machine. Consequently, the use of such a hook exchanger is limited to industrial flat-bed, embroidery, or sewing machines. Use in a free-arm household sewing machine is not possible.
From EP-A1-0829565, an automatic bobbin exchanger for a flat-bed sewing machine is further known, for which the empty bobbin together with the bobbin case is discharged from the hook with a handling device that can move on a curved track, the bobbin and bobbin case are fed to a revolver carrying several bobbin cases with bobbins, and then this revolver supplies a bobbin case with a full bobbin, which is brought to the hook. This arrangement can also be used only in commercial machines.
From DE-A1 199 07 007, an adjustable hook is further known, which can be shifted in the axial direction in the range of a few tenths of a millimeter in order to compensate for production inaccuracies after the assembly of the sewing machines. This minimal forwards or backwards sliding of the hook does not simplify the bobbin exchange, because the hook cannot be moved away from the lower arm.